1. Field of the Invention
The present invention relates to an automatic developing apparatus for a photosensitive lithographic printing plate and to a method of replenishing a replenisher for developer for the apparatuses, and, in particular, to such a method as to minimize the fluctuation of developer sensitivity due to changes in developing conditions.
2. Description of the Related Art
In general, as a representative method of controlling the developer sensitivity in an automatic developing apparatus for photosensitive lithographic printing plates, there is adopted a method replenishing a replenisher for developer (hereinafter, just referred to as xe2x80x9creplenisherxe2x80x9d) with time and processing, which replenishes the replenisher with time to a developer tank that a developer is stored, measures the plate area of the processed plates, and replenishes an amount of the replenisher corresponding to the measured value (hereinafter, referred to as xe2x80x9cplate area-based replenishing methodxe2x80x9d).
However, the plate area-based replenishing method requires a device for measuring a plate area of the lithographic plate in a developing part of the automatic developing apparatus, thus causing the structure of the developing apparatus complicated and expensive.
Further, it is difficult to judge whether a single surface or the both surfaces of the lithographic plate are processed, (hereinafter, referred to as xe2x80x9csingle surface/dual surfacexe2x80x9d.) and the type of plate (note that there are various kinds of plates differing in coated amount of the photosensitive layer). Thus, in case that the appropriate replenisher amount will change depending on the plate area, the single surface/dual surface, and the type of plate, there is a problem that it makes difficult to appropriately replenish the replenisher.
On the other hand, there is conventionally disclosed in JP-A-64-21451 (the term xe2x80x9cJP-Axe2x80x9d as used herein means a Japanese Patent Unexamined Publication), a method replenishing the replenisher for an automatic developing apparatus for photosensitive lithographic printing plates, which measures the electric conductivity of the developer, compares the measured value with the calculated value that has been experimentally determined for the optimum sensitivity, and replenishes the replenisher in the case where the measured value is smaller than the calculated value. (Hereinafter, this method will be referred to as xe2x80x9cconductivity-based replenishing methodxe2x80x9d.)
The conductivity-based replenishing method can replenish the appropriate amount of the replenisher and can appropriately keep the developer sensitivity, even with the changes in plate area, single surface/dual surface, or type of lithographic plate to be processed.
However, it should be noted that the developer conductivity is affected (rises) by natural evaporation of water from the developer. Accordingly, when natural evaporation of water is promoted due to the affect of the installed conditions of the automatic developing apparatus or the like, an appropriate replenishing amount of the replenisher will be changed.
The aforementioned conductivity-based replenishing method cannot deal with the changes of the appropriate replenishing amount of the replenisher due to the natural evaporation of water. Thus, when the natural evaporation of water is increased, the appropriate replenishment is not realized, thus failing in keeping the developer sensitivity appropriately.
Moreover, the electric conductivity of the developer exhausted by carbon dioxide absorbed in elapsed time differs from that of the one exhausted by plate processing when the sensitivity of the two are recovered to their proper values. For example, a silicate-type processing agent exhibits 65 mS/cm when recovered from CO2 fatigue in contrast to 55 mS/cm when recovered from plate processing, and a non-silicate-type processing agent exhibits 56 mS/cm when recovered from CO2 fatigue in contrast to 39 mS/cm when recovered from plate processing. Therefore, if the frequency of processing, e.g., the processed amount per day changes, the electric conductivity for its optimal sensitivity tends to shift from the reference conductivity value set up in advance, thus it becomes impossible to keep the developer sensitivity appropriately.
By taking into account those situations described above, the object of the present invention is to provide an automatic developing apparatus and a method of replenishing the replenisher for said apparatuses, which can minimize the fluctuation of developing sensitivity against the changes in developing conditions, while using an economic and simple developing unit of the automatic developing apparatus, to thereby perform a stable development.
The purpose of the present invention can be achieved with the following apparatuses and methods.
(1) An automatic developing apparatus for photosensitive materials, includes:
a developer tank storing a developer;
a replenishing unit replenishing a predetermined amount of a replenisher for developer to maintain a developing activity of the developer in the developer tank;
a memory for memorizing a first preset replenishing condition of the replenisher to compensate the reduction of the developing activity during working and/or stopped period, and a second preset replenishing condition of the replenisher to compensate the reduction of developing activity caused by the processing of the photosensitive materials;
a calculating unit calculating a replenisher replacement ratio being a ratio that a charged solution of the developer is replaced by at least one of the replenisher and a diluent replenished for reducing an electric conductivity of the developer;
an electric conductivity sensor measuring the electric conductivity of the developer; and
a diluent replenishing unit replenishing the diluent to the developer tank until the electric conductivity becomes lower than an electric conductivity target value previously calculated from the replenisher replacement ratio, when the measured value of electric conductivity exceeds the target value.
(2) The automatic developing apparatus according to (1), wherein the electric conductivity target value is calculated from the replenisher replacement ratio, and one of the following values:
a) a dilution ratio of the sum of a diluent for diluting the replenisher and the diluent replenished for lowering the electric conductivity of the developer in the developer tank, relative to the replenisher, and
b) a ratio of the integral amount of the replenisher which is replenished to compensate the reduction of the developing activity during working and/or stopping period, relative to the product of the replenisher replacement ratio with the amount of the developer.
(3) The automatic developing apparatus according to (1), wherein at least one of the developer tank and the automatic developing apparatus is structured to suppress air ventilation so that the CO2 concentration of the air in a direct contact with the developer in the developer tank is kept below 300 ppm.
(4) A method of replenishing a replenisher for a developer in an automatic developing apparatus for photosensitive materials, includes the steps of:
a) replenishing a replenisher for developer based on a first predetermined replenishing condition so as to compensate the reduction of a developing activity during working and/or stopped period;
b) replenishing the replenisher based on a second predetermined replenishing condition so as to compensate the reduction of the developing activity caused by the processing of the photosensitive materials;
c) measuring an electric conductivity of the developer replenished with the replenisher in the steps a) and b); and
d) replenishing a diluent into the developer until the electric conductivity of the developer falls below an electric conductivity target value predetermined by using a replenisher replacement ratio, when the measured value of the electric conductivity of the developer exceeds the target value.
(5) The method according to (4), wherein the electric conductivity target value is calculated from the replenisher replacement ratio, and one of the following values:
a) a dilution ratio of the sum of a diluent for diluting the replenisher and the diluent replenished for lowering the electric conductivity of the developer in the developer tank, relative to the replenisher, and
b) a ratio of the integral amount of the replenisher which is replenished to compensate the reduction of the developing activity during working and/or stopping period, relative to the product of the replenisher replacement ratio with the amount of the developer.
In the present invention, the xe2x80x9creplenisher for developerxe2x80x9d represents a processing solution to be replenished for maintaining a constant developing performance. The replenisher for developer includes a solution regulated by diluting an undiluted replenisher with a diluent such as water, or a replenisher which can use without dilution as it is. Further, as to a replenishing method, the replenisher regulated by previously diluting the undiluted replenisher may be replenished to the developer tank, or the undiluted replenisher and the diluent may be directly replenished to the developer tank. In addition, when using the undiluted replenisher and the diluent, the integral amount of the replenisher is obtained by the sum of the undiluted replenisher and the diluent.
In the present invention, the electric conductivity of the developer can be measured with any device well known in the art, including an AC conductivity meter, an AC bridge meter and other types of conductivity meters.
In addition, although an optimal condition of a measured current value and an oscillating frequency or the like of the measuring device depends on compositions of the developer and the like, but from the viewpoints of device protection and preventing the electrolysis of the aqueous developer, it is preferable that the current value makes low to some extent, that is, from several hundred mA to several xcexcA.
Further, from the viewpoints of the electrostatic capacity component of the developer, it is preferable that the frequency is from several hundred Hz to several hundred kHz.
The electric conductivity of the developer containing electrolytes depends on the temperature of the aqueous solution, and the electric conductivity decreases as the temperature rises. Hence, it is more preferable to measure the electric conductivity with a measuring device equipped with a temperature sensor and a temperature compensating circuit. Further, the controller for replenishment can compensate the temperature by converting an actually measured liquid resistance value and liquid temperature into the electric conductivity value at the predetermined temperature.
The sensor of the AC conductivity meter, the AC bridge meter, or other types of conductivity meters may be placed at any place where the sensor can be immersed in the developer at the measuring time and can measures its AC conductivity value of the developer. Preferably, the sensor can be placed inside the developer circulation system of the automatic developing apparatus, particularly, in the developer tank or in the circulation pipe.
As the detecting device, a well-known measuring cell containing electrodes made of platinum, stainless steel, or the like can be used.
Next, a description will be given of a developer and a replenisher applicable to the present invention.
1. Developer
The developer and the replenisher used in the present invention is aqueous alkaline solution with pH 9.0xcx9c13.5, and more preferably pH 10.0xcx9c13.3.
Conventionally known aqueous alkaline solutions can be used as such a developer or a replenisher. For example, inorganic base materials such as sodium or potassium silicate, trisodium, tripotassium or triammonium phosphate, disodium, dipotassium or diammonium hydrogenphosphate, sodium, potassium or ammonium bicarbonate, sodium, potassium or ammonium carbonate, sodium potassium or ammonium bicarbonate, sodium, potassium or ammonium borate, sodium, potassium, ammonium or lithium hydroxide, etc., and organic ones such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamide, diisopropanolamine, ethyleneimine, ethylenediamine, pyridine, etc. can be used.
Among these alkali agents, preferable ones are sodium and potassium silicate, because changing the ratio of silicon dioxide SiO2 to alkaline metal oxide M2O both of which constitute these salts as well as the concentration can control the pH as well as the developing activity. In general, the silicate composition is expressed by the molar ratio of SiO2 to M2O([SiO2]/[M2O]). For example, an aqueous solution of potassium silicate having a molar ratio of SiO2 to M2O of 0.5-2.0 (i.e., [SiO2]/[M2O]=0.5-2.0), and the content of SiO2 in said solution being 1-4% by weight, is preferably used in the present invention.
Further, more preferable alkali agents used for the alkaline developer include those used for buffer solutions comprising a pair of weak acid and weak base. As weak acids used for such buffer solutions, those having an acid dissociation constant (pKa) of 10.0-13.3, more preferably 11.0-13.1, are suited. For example, sulfosalicylic acid having the third dissociation constant of 11.7 can be preferably used. Thus, polybasic acids at least one dissociation constant of which lies in the above-cited range can be applicable to the present invention.
Suitable weak acids can be chosen among those described in xe2x80x9cIonization constants of organic acids in aqueous solutionxe2x80x9d (Pergamon Press), etc., including, for example, alcohols such as 2,2,3,3-tetrafluoropropanol-1 (pKa=12.74), trifluoroethanol (12.37), trichloroethanol (12.24), etc., aldehydes such as pyridine-2-aldehyde (12.68), pyridine-4-aldehyde (12.05), etc., saccharides such as sorbitol (13.0), sucrose (12.7), 2-deoxyribose (12.61), 2-deoxyglucose (12.51), glucose (12.46), galactose (12.35), arabinose (12.34), xylose (12.29), fructose (12.27), ribose (12.22), mannose. (12.08), L-ascorbic acid (11.34), etc., compounds having one or more phenolic hydroxy groups such as salicylic acid (13.0), 3-hydroxy-2-naphthoic acid (12.84), catechol (12.6), gallic acid (12.4), sulfosalicylic acid (11.7), 3,4-dihydroxybenzenesulfonic acid (12.2), 3,4-dihydroxybenzoic acid (11.94), 1,2,4-trihydroxybenzene (11.82), hydroquinone (11.56), pyrogallol (11.34), resorcinol (11.27), etc., oximes such as 2-butanone oxime (12.45), acetoxime (12.42), 1,2-cycloheptanedionedioxime (12.3), 2-hydroxybenzadehyde oxime (12.10), dimethylglyoxime (11.9), ethanediamide dioxime (11.37), acetophenone oxime (11.35), etc., amino acids such as 2-quinolone (11.76), 2-pyridone (11.65), 4-quinolone (11.28), 4-pyridone (11.12), 5-aminovaleric acid (10.77), 2-mercaptoquinoline (10.25), 3-aminopropionic acid (10.24), etc., nucleic acid-related compounds such as fluorouracil (13.0), guanosine (12.6), uridine (12.6), adenosine (12.56), inosine (12.5), guanine (12.3), cytisine (12.2), cytosine (12.2), hypoxanthine (12.1), xanthine (11.9), etc., other weak acids such as diethylaminomethylphosphonic acid (12.32), 1-amino-3,3,3-trifluorobenzoic acid (12.29), isopropylidenediphosphonic acid(12.10), 1,1-ethylidenediphosphonic acid (11.54), 1,1-ethylidenediphosphonic acid-1-hydroxy (11.52), benzimidazole (12.86), thiozenzamide (12.8), pycolinethioamide (12.55), barbituric acid (12.5), etc.
Strong bases to be combined with the weak acids cited above include sodium, ammonium, potassium or lithium hydroxide.
Each of these bases can be used alone or in combination with each other.
Among the alkaline buffer agents mentioned above, preferable ones are the combinations of either of sulfosalicylic acid, salicylic acid, sucrose or sorbitol with sodium or potassium hydroxide. More preferable combinations comprise sorbitol and potassium or sodium hydroxide.
These alkali agents are used in such a manner as to realize preferable pH values by controlling their concentrations as well as combinations.
In the developer and the replenisher used in the present invention, various surfactants can be contained in order to promote development, disperse development scum, or to enforce the ink receptivity of the image area of the printing plate. Preferable surfactants include anionic, cationic, nonionic or amphoteric compounds.
Preferable examples of such surfactants include nonionic ones such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyrylphenyl ethers, polyoxyethylene polyoxypropylenealkyl ethers, partial fatty acid esters of glycerin, partial fatty acid esters of sorbitan, partial fatty acid esters of pentaerithritol, monofatty acid esters of propylene glycol, partial fatty acid esters of sucrose, partial fatty acid esters of polyoxyethylene sorbitan, partial fatty acid esters of polyoxyethylene sorbitol, fatty acid esters of polyethylene glycol, partial fatty acid esters of polyglycerin, polyoxyethylene-added castor oil, partial fatty acid esters of polyoxyethylene glycerin, fatty acid diethanolamides, N,N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, fatty acid esters of triethanolamine, trialkylamine oxide, etc.; anionic surfactants such as the salts of the following acids; fatty acid, abietic acid, hydroxyalkanesulfonic acid, alkanesulfonic acid, dialkylsulfosuccinic acid ester, straight and branched chain alkylbenzenesulfonic acid, alkylnaphthalenesulfonic acid, or alkylphenoxypolyoxyethylene propylsulfonic acid, polyoxyethylene alkylsulfophenyl ethersalt, sodium salt of N-methyl-N-oleyltaurine, bi-sodium salt of N-alkylsulfosuccinic acid monoamide, salts of petroleum sulfonic acid, sulfonated tallow, sulfate salts of fatty acid alkyl ester, alkylsulfate salts, polyoxyethylene alkyl ether sulfate salts, sulfate salts of fatty acid monoglyceride, polyoxyethylene alkylphenyl sulfate, poyoxyethylene styrylphenyl ether sulfate salts, alkylphosphate salts, polyoxyethylenealkyl ether phosphate salts, polyoxyethylene alkylphenyl ether phosphate salts, partially saponified styrene/maleic anhydride copolymers, partially saponified olefin/maleic anhydride copolymers, formaldehyde condensation products of naphthalenesulfonic acid salt, etc.; cationic surfactants such as quaternary ammonium e.g., alkylamine salts, tetrabutylammonium bromide, etc., polyoxyethylene alkylamine salts, polyethylene polyamine derivatives, etc.; amphoteric surfactants such as carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfonic acid esters, imidazolines, etc. Among surfactants described above, xe2x80x9cpolyoxyethylenexe2x80x9d group is replaceable to xe2x80x9cpolyoxyalkylenexe2x80x9d including xe2x80x9cpolyoxymethylenexe2x80x9d, xe2x80x9cpolyoxypropylenexe2x80x9d, xe2x80x9cpolyoxybutylenexe2x80x9d, etc., and those having the replaced groups can also be included in the scope of the invention.
More preferable surfactants are fluorine-containing surfactants which include in their molecular structure a perfluoroalkyl group. Such surfactants include anionic ones such as perfluoroalkylcarboxylic acid salts, perfluoroalkylsulfonic acid salts, perfluoroalkylphosphoric acid esters, etc., amphoteric ones such as perfluoroalkylbetaine, etc., cationic ones such as perfluoroalkyltrimethylammnonium salts, etc., nonionic ones such as perfluoroalkylamine oxides, perfluoroalkylethylene oxide adducts, oligomers having perfluoroalkyl groups and hydrophilic groups, oligomers having perfluoroalkyl groups and oleophilic groups, oligomers having perfluoroalkyl groups, hydrophilic and oleophilic groups, urethanes having perfluoroalkyl groups and oleophilic groups, etc.
The surfactants described above can be used individually or in combination of two or more kinds of them in the concentration range of 0.001 to 10% by weight, or in a more preferable range of 0.01 to 5% by weight of the developer.
Various development stabilizing agents can be incorporated in the developer and the replenisher of the present invention, including polyethylene glycol adducts of sucrose alcohol disclosed in JP-A-6-282079, tetraalkylammonium salts such as tetrabutylammonium hydroxide, etc. phosphonium salts such as tetrabutylphosphonium bromide, etc, and iodonium salts such as diphenyliodonium chloride, etc.
Further, the anionic or the amphoteric surfactants disclosed in JP-A-55-51324, the water soluble cationic polymers disclosed in JP-A-55-95946, and the amphoteric polymer electrolytes disclosed in JP-A-56-142528 can be used.
Moreover, alkylene glycol-added organic boron compounds disclosed in JP-A-59-84241, water soluble surfactants comprising polyoxyethylene/polyoxypropylene block type disclosed in JP-A-60-111246, alkylenediamines substituted with polyoxyethylene polyoxypropylene disclosed in JP-A-60-129750, polyethylene glycol having weight-averaged molecular weight of not less than 300 disclosed in JP-A-61-215554, fluorine-containing surfactants having a cationic group disclosed in JP-A-63-175858, the water soluble ethylene oxide-added compounds obtained by adding 4 or more moles of ethylene oxide to acids or alcohols disclosed in JP-A-2-39157, water soluble polyalkylene compounds, etc.
If needed, organic solvents can be added to the developer and the replenisher of the present invention. Suitable organic solvents should have a solubility to water of 10% by weight or less, more preferable 5% by weight or less. Examples of such solvents include 1- and 2-phenylethanol, 3-phenyl-1-propanol, 4-phenyl-1-butanol, 4-phenyl-2-butanol, 2-phenyl-1-butanol, 2-phenoxyethanol, 2-benzyloxyethanol, o-methoxybenzyl alcohol, m-methoxybenzyl alcohol, p-methoxybenzyl alcohol, benzyl alcohol, cyclohexanol, 2-, 3- and 4-methylcyclohexanol, N-phenylethanolamine, N-phenyldiethanolamine, etc. A suitable range for the content of such organic solvents is from 0.1 to 5% by weight of the total amount of the working solution. The content has a close relation to the amount of the surfactant in use; with the increase of organic solvent, the amount of surfactant should preferably be increased. When only a small amount of surfactant is used in the presence of a large amount of organic solvent, the organic solvent will sometimes not be perfectly dissolved in the composition, thus failing in securing a desirable level of developing capability.
The developer and replenisher compositions of the present invention can further contain reducing agents in order to prevent lithographic printing plates from staining. Reducing agents are particularly effective for the development of negative-working photosensitive lithographic printing plates containing photosensitive diazonium salt compounds. Particularly preferred organic reducing agents include phenolic compounds such as thiosalicylic acid, hydroquinone, Methol (N-methylaminophenol), methoxyquinone, resorsine, 2-methylresorsine, etc. amine compounds such as phenylenediamine, phenylhydrazine, etc. Particularly preferred inorganic reducing agents include the sodium, potassium and ammonium salts of inorganic acid such as sulfurous, hydrogensulfurous, phosphorous, monohydrogenphosphorous, dihydrogenphosphorous, thiosulfuric, dithionous acid, etc. Among these reducing agents, the most preferable one is sulfite salts. The preferable range for the content of the reducing agent is from 0.05 to 5% by weight of the working developer.
The developer and replenisher compositions of the present invention can further contain organic carboxylic acids. Preferable acids are aliphatic and aromatic carboxylic acids with 6-20 carbon atoms. Preferable aliphatic acids include caproic, enanthic, capryl, lauric, myristic, palmitic, stearic acids, etc., particularly suitable ones being C8-12 alkanoic acids. Unsaturated fatty acids containing double bonds in their carbon chain can be used. Branched chain fatty acids can also be used.
Suitable aromatic carboxylic acids are those comprising benzene ring, naphthalene ring, anthracene ring substituted with a carboxyl group, exemplified by o-chlorobenzoic acid, p-chlorobenzoic acid, o-hydroxybenzoic acid, p-hydroxybenzoic acid, o-aminobenzoic acid, p-aminobenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, gallic acid, 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1- and 2-naphthoic acid, etc. Among these, hydroxynaphthoic acid is one of the most suitable aromatic acids.
The above described aliphatic and aromatic carboxylic acids can be preferably used in the form of sodium, potassium or ammonium salt to secure a high solubility to water. There is no special limitation on the content of organic carboxylic acid in the developer composition of the present invention, but, in general, contents below 0.1% by weight cannot exert a sufficient effect; on the other hand, when the acid content exceeds 10% by weight, the effect is saturated, and tends to hinder the solution of other additives. Accordingly, the practical range lies between 0.1 and 10% and more preferably 0.5 and 4% by weight of the working developer.
Antiseptics can be added to the developer, washing water or finishing liquid. Known antiseptics for fabric, wood processing, food, cosmetic, agricultural chemical, etc. can be used. Examples include quaternary ammonium salts, monovalent, bivalent or polyvalent phenol derivatives, imidazole derivatives, pyrazolopyrimidine derivatives, monovalent naphthol, carbonates, sulfone derivatives, organic tin compound, cyclopentane derivatives, phenyl derivatives, phenol ether derivatives, phenol ester derivatives, hydroxylamine derivatives, nitrile derivatives, naphthalines, pyrrole derivatives, quinoline derivatives, benzothiazole derivatives, secondary amines, 1,3,5-triazine derivatives, thiadiazole derivatives, anilide derivatives, pyrrole derivatives, halogen derivatives, dihydric alcohol derivatives, dithiols, cyanic acid derivatives, thiocarbamide derivatives, diamine derivatives, isothiazole derivatives, monohydric alcohols, saturated aldehydes, unsaturated monocarboxylic acids, saturated and unsaturated ethers, lactones, amino acid derivatives, hydantoins, cyanuric acid derivatives, guanidine derivatives, pyridine derivatives, saturated monocarboxylic acids, benzenecarboxylic acid derivatives, hydroxycarboxylic acid derivatives, biphenyl, hydroxamic acid derivatives, aromatic alcohols, halogenophenol derivatives, benzenecarboxylic acid derivatives, mercaptocarboxylic acid derivatives, quaternary ammonium salt derivatives, triphenylmethane derivatives, hinokitiol, furan and benzofuran derivatives, acridine derivatives, isoquinoline derivatives, arsine derivatives, thiocarbamic acid derivatives, phosphoric acid esters, halogenated benzene derivatives, quinone derivatives, benzenesulfonic acid derivatives, monoamine derivatives, organic phosphoric acid esters, piperadine derivatives, phenazine derivative, pyrimidine derivatives, thiophanate derivatives, imidazoline derivatives, isoxazole derivatives, ammonium salt derivatives, et. Particularly suited anticeptics are the salts of pyridinethiol-1-oxide, salicylic acid and its salts, 1,3,5-trishydroxyethylhexahydro-S-triazine, 1,3,5-trishydroxymethylhexahydro-S-triazine, 1,2-benzisothiazoline-3-one, 5-chloro-2-methyl-4-isothiazoline-3-one and 2-bromo-2-nitro-1,3-propanediol. The addition levels of these antiseptics are determined so as for the antiseptics to work in a stable and effective manner against bacteria, mold, yeast fungi, etc., depending on the kinds of bacteria, etc. A preferable range is usually 0.01-4% by weight. In general, combined two or more kinds of antiseptics are preferably used together to protect the developer from various kinds of bacteria, mold, etc.
The developer and replenisher compositions used in the present invention can further contain still other ingredients such as anti-forming agent, water softener, etc., depending on the need. Softeners for hard water include, for example, polyphosphoric acid and its sodium, potassium or ammonium salt, amino-polycarboxylic acid such as ethylenediamineteteraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, hydroxyethylethylenediaminetriacetic acid, nitrylotriacetic acid, 1,2-diaminocyclohexanetetraacetic acid, 1,3-diamino-2-propanol tetraacetic acid, etc., sodium, potassium or ammonium salt of the amino-polycarboxylic acids described above, aminotri(methylene phosphonic acid), ethylenediamine-tetra(methylene phosphonic acid), diethylenetriaminepenta(methylene phosphonic acid), triethylenetetraminehexa(methylene phosphonic acid), hydroxyethylethylene-diaminetri(methylene phosphonic acid) and 1-hydroxyethane-1,1-diphosphonic acid and sodium, potassium or ammonium salt of the phosphonic acids cited above.
A preferable range for the concentration of such a softener depends on its chelating capability as well as the hardness of the water in concern; generally speaking, based on the working developer, 0.01-5% by weight and more preferably 0.01-0.5% by weight is recommended. Lower concentration levels than the described range fail to exert a sufficient softening effect; on the other hand, higher addition levels tend to have adverse effects on developed images such as density drop, etc.
The remaining part of the developer and the replenisher consists of water, to which still various additives known in the art can be added.
From the viewpoint of the transportation, the developer and the replenisher of the present invention take a condensed form in which they have an increased concentration of ingredients to be diluted with water in use. The degree of condensation is determined so as to cause neither phase separation nor deposition of the ingredients. The temperature of the developer should be kept at 15-40xc2x0 C., and more preferably 20-35xc2x0 C. The developing time is preferably 5-60 sec, and more preferably 7xcx9c40 sec.
The method of the invention can be applied not only to the above-cited developers, but also to those described in EP0836120A1, EP0908785A, EP0908306A, EP0914941A1, JP-A-11-327163 and JP-A-11-327160 and Japanese Patent Application No. 2000-255670.
Next, photosensitive lithographic printing plates used in the present invention will be described.
A type of positive-working image recording material is proposed in JP-A-7-285275, JP-A-11-119419 and Japanese Patent Application 11-182751 in which the material can record images via an infrared laser exposure. The photosensitive material consists of a binding agent such as cresol resin, a substance that generates heat by absorbing light, and another substance that is thermally decomposable such as quinonnediazide and which substantially prevents said binding agent from dissolving in the developer when not decomposed. In such a positive-working material, at exposed areas, the substance generating head by absorbing light generates head, thus causing the exposed areas to dissolve.
Furthermore, JP-A-7-20625, JP-A-11-218903, Japanese patent application Nos. 11-308286 and 11-332936 disclose a type of negative-working image recording material comprising a compound that generates acid upon the decomposition by light or heat, a cross-linking agent that works by the presence of acid, at least one kind of alkali-soluble resin, and an infrared light absorbing agent. In such a negative-working image recording material, at exposed areas, the substance generates heat by absorbing light, the above compound generates acid by decomposing by the heat, and the acid thus formed promotes the cross-linking of the alkali-soluble resin with the cross-linking agent, to thereby perform an image recording.
The present invention can use such image recording materials described above as a lithographic printing plate. To form lithographic printing plates, the image recording on lithographic printing plates is performed by an infrared laser exposure, which are subjected to heat treatment, if needed, and then to perform a development proceeding.
The present invention is also applicable to the processing of the photosensitive lithographic printing plates based on the photopolymer compositions as disclosed in Japanese Patent Application Hei.10-251521, JP-A-2000-39724 and Japanese Patent Application 2000-276811. The photosensitive lithographic printing plates based on the photopolymer compositions consist of, on a substrate that an aluminum plate is subjected to a hydrophilic proceeding, a photo-polymerizable layer containing a compound having an ethylenic double bond capable of addition polymerization and a polymer having a cross-linkable group in its side chain. In the present invention, such a type of lithographic plate is exposed imagewise with laser light and then is developed.
The present invention is also applicable to the processing of the positive-working photosensitive lithographic printing plates disclosed in JP-A-9-274324, JP-A-2000-231188 and Japanese Patent Application No.2000-13656, having been in a wide use in the conventional art. This type of lithographic plate consists of an aluminum plate as a support body on which a photosensitive layer containing an o-quinonediazide compound. O-quinonediazide compounds are known to be converted to carboxylic acids by UV exposure, thus the layer can be developed with an aqueous alkaline solution to cause a removal of the exposed areas of the photosensitive layer, whereby the support body surface is exposed. The exposed support surface of the aluminum support body, which is hydrophilic, at the exposed (non-image portion) areas holds water by the development and repels oil based ink on the printer. On the other hand, the image areas where the photosensitive layer remains accept oil based ink and repels water. Usually, in the photosensitive layer of such positive-working type lithographic plates is incorporated a cresol-novolac resin as the binder for the o-quinonediazide compound. The method of the present invention is applicable to the proceeding of the negative-working photosensitive lithographic plate, which is disclosed in JP-A-7-295212 and Japanese Patent Application No. 2000-103135.